Effectiveness of Safe Patient Handling Equipment and Techniques: A Review of Biomechanical Studies

Objective This review aimed to evaluate all studies that have evaluated the biomechanical effects when using assistive devices. Introduction The physical demands of patient handling activities are well known. One safety strategy for the reduction of the physical risks is use of assistive devices. Method The search process identified articles published in English-speaking journals through Google Scholar, Medline, and ISI Web of Science. The included 56 studies contained a biomechanical assessment of a patient handling activity with assistive devices. Results The biomechanical effects included four groups: changes in body posture (spinal, other joints), subjective assessment (force, effort, discomfort), measured force (hand force, ground reaction force, spine force, joint torque), and physiological measures. The evidence showed caregivers benefited from using lift hoists, air-assisted devices, and to a lesser extent friction reducing devices for lateral transfers and repositioning, while floor and ceiling lifts were most effective for patient transfers. Some gaps were noted in the evidence and other handling tasks such as sit-to-stand, turning patient in bed, limb lifting, and repositioning and some more high hazard activities like supporting people with limited balance and those that fall need to be investigated with respect to biomechanical outcomes. Conclusion There is a growing level of biomechanical evidence to support the use of assistive devices for many patient-handling tasks, but the benefits of equipment use in some transfers remain uninvestigated. Practical Application Evidence indicates the best way to lift patients safely is with floor or ceiling lifts, and air-assisted devices for lateral and repositioning tasks.


Introduction
The physical demands required to assist patient movement are both a common nursing activity and have long been recognized (Garg & Owen, 1992;Jäger et al., 2013;Marras et al., 1999).The relationship between the frequent exposure to high load patient handling tasks is a known contributory factor to the musculoskeletal problems of care workers (Davis & Kotowski, 2015).The developing knowledge and practices consider the use of assistive devices as a recognized control measure to reduce the burden on the care worker (Anderson et al., 2014).The direct reduction of force requirements or the replacement of human effort with mechanical means has received strong support and wide implementation.The range of devices commonly seen in care situations can include: the replacement of full weightlifting with a powered lifter (Alamgir et al., 2009;Dutta et al., 2012), the reduction of forces for horizontal transfers with friction reduction devices (Waters, 2011), patient turning (Budarick et al., 2020), or the use of a powered bed to assist repositioning (Zhou & Wiggermann, 2021).
Several literature reviews have cumulated the body of evidence surrounding both the deleterious effects of patient handling and the possible benefits of a range of available interventions (Al Johani & Pascua, 2019;Mayeda-Letourneau, 2014;Nelson & Baptiste, 2006;Teeple et al., 2017).It should be noted that the reported evidence for the use of safety interventions in patient handling risk reduction is in a development phase and early reviews found only small numbers of highquality papers for inclusion (Bos et al., 2006;Dawson et al., 2007;Martimo et al., 2008), a more inclusive review reported a much higher number of studies (Hignett et al., 2003) but acknowledges a different and less stringent inclusion criteria.The growth of evidence over a decade is reported in better quality of data and analysis in more recent studies (Anderson et al., 2013;Teeple et al., 2017).Even with the increased knowledge that assistive devices can significantly reduce the load on caregivers, some studies still show that the use of devices is not universal (Koppelaar et al., 2011).
Previous reviews of safe patient handling have focused on the effectiveness of programs and lift equipment in reducing musculoskeletal disorders (MSDs) in healthcare system (Al Johani & Pascua, 2019, Hignett et al., 2003;Mayeda-Letourneau, 2014;Nelson & Baptiste, 2006;Teeple et al., 2017).To understand the effectiveness of safe patient handling equipment, a comprehensive assessment of the studies that have investigated the impact on biomechanical responses within the body during safe patient handling tasks is needed.The aim of the review is to collectively report all the biomechanical effects that have been assessed when using assistive devices and lifting training (e.g., proper lifting technique) across all the range of regularly performed patient transfers and movement activities (Crowshaw and Fray, 2018;Smith et al., 2011).Biomechanical assessments can provide a better understanding of the results as compared to epidemiological studies with respect to safe patient handling equipment being protective of MSDs.The accumulated information could be used to further support the purchase, implementation, and use of assistive devices to better protect care workers from musculoskeletal disorders.

Review Approach
The research team searched for published articles (prior to March 2023) that investigated biomechanical outcomes (either subjective or objective) when assessing safe patient handling devices and techniques (e.g., proper lifting).The review was completed using the PRISMA 2020 checklist to ensure quality and reproducibility (Page et al., 2021).Epidemiological studies that did not include biomechanical outcomes were eliminated from consideration, specifically studies that focused on reduced injuries and reported cases were excluded.Others have provided reviews that focused on these outcomes (Anderson et al., 2013;Bos et al., 2006;Dawson et al., 2007;Martimo et al., 2008;Teeple et al., 2017).

Article Inclusion Criteria
While the following will provide the details of inclusion, the inclusion criteria was any biomechanical study that evaluated patient handling equipment and proper lifting techniques.A search for all articles published in English-speaking journals was undertaken through Google Scholar, Medline, and ISI Web of Science.For each of the search engines, the search strategy was to search for the same string of keywords with no filters.The search words included "safe patient handling," which yielded 13,444 articles.All duplicate articles among the search results were removed.The remaining articles were further screened (by KD) where the title and abstract were assessed for inclusion of biomechanical outcomes (generally) as well as assessment of lifting equipment and proper manual lifting training technique.All articles that meet basic biomechanical assessment were downloaded for additional evaluation of the quality of the study and inclusion of at least one of the specific biomechanical outcomes.Reviews and epidemiological studies investigating the use of lift equipment and safe patient handling programs only were not included in the current review.
As a result of this initial review, included article count was reduced to 102 relevant articles based on the criteria that some type of biomechanical assessment, either objective or subjective, was utilized and described in the abstract.One of the following outcomes had to be included as an outcome variable to be included in the review: spine posture (flexion, lateral flexion, twist in degrees), whole body motion based on motion capture (joint angles in degrees), specific body movement by other joint position method, physiological measures (fatigue with changes of median frequency of muscle activation, oxygen consumption in ml/min, energy expenditure in Kcal), subjective forces (rating of perceived exertion in Likert scale), discomfort (Likert scale, usually 1-10), ground reaction force (three-dimensional force in N), hand or applied force (force in N), muscle activity (normalized in %MVC), spine loads three dimensional loads in N), and joint torque (moment in Nm).These categories served as the classifications to group the studies for synthesis.Each category included specific biomechanical measures as defined by the individual studies.
The next step was to complete a thorough review of the remaining articles to ensure biomechanical assessment and inclusion (completed by KD and verified independently by MF).Articles were only eliminated if they did not have a biomechanical assessment in one or more of the above categories or did not assess lift equipment/proper lifting training.Finally, the reference lists for all relevant articles were scanned to identify any missing articles, which the above process was undertaken for those identified articles.Starting with a broad search of "safe patient handling" and narrowing with the biomechanical outcomes ensured a broad and comprehensive assessment of the literature for patient handling equipment and proper lifting training.
In total, 57 articles were included in the review and underwent the quality assessment (completed by KD and verified by MF) (see below for details of quality assessment).The review included all relevant articles with no exclusion due to poor quality, although quality was discussed.Figure 1 provides a schematic of the inclusion process.

Quality Assessment of Papers
Mixed Methods Appraisal Tool (MMAT), developed by Pluye and Hong (2014), was used to rate the quality of each article.Based on the criteria for qualitative and quantitative random designs, quantitative nonrandom designs, and mixed methods, each article was rated and scored (by KD, and independently verified by MF).The main questions rated were: (1) Are the participants representative of the target population?(2) Are there complete outcome data?(3) Are the confounders accounted for in the design and analysis?(4) Are outcome assessors blinded to the intervention provided?and (5) Did the participants adhere to the assigned intervention?The articles were then quantified based on the score (each yes for the questions associated with the study design) and whether measurements were valid.The measurement evaluation was based on criteria: sufficient numbers of participants (greater than 20), measures were validated in literaturetechniques well established with reliability quantitative measures with calibrated equipment and techniques, using realistic patients-assessments using standardized, noncompliant, realistic patients, and reliable equipment-use of sensitive equipment and surveys.These additional criteria assess the quality of measures and whether conditions were realistic to healthcare settings.Each of the criteria was rated as satisfactory/yes (1) or not satisfactory/no (0) with the total scores providing the overall quality assessment.Based on these scores, the articles were classified in the following quality categories: (1) low (score 0-1), (2) low-medium (score 2-3), ( 3) medium (score 4-5), (4) medium-high (score 6-7), and ( 5) high (score 8-9).

Synthesis Methods for Review
In order to evaluate all existing literature for safe patient handling equipment and proper lifting training, all 57 articles were included with none being eliminated.To understand the details of studies included in the review, Table 1 included authors, dates of publication, study population, country where study was collected, study design, and the quality rating of the study was constructed.The study design was particularly important in synergizing the results of the studies as it indicated the outcome measures used and the type of equipment/training.For each of the studies, the team tabulated the results for each biomechanical outcome variable that was measured as a function of the safe patient handling equipment and lifting technique training (see Appendix for the complete results).Based on the results in the tables in the Appendix, a summary table was developed to  provide a more global summary of the results so that a more complete assessment of the existing results could be identified (see Table 2).

FINDINGS AND DISCUSSION
Table 2 provides a summary of the results for the different modalities of safe patient handling.
One interesting finding was that there are few studies (4) reporting a negative result (e.g., increase in outcome variable) for any safe patient handling modality.This indicates that in the worst case, the patient handling equipment was equivalent to manual lifting.There was one high, six medium-high quality studies, thirty-six medium quality studies, and thirteen low-medium quality studies, and one low quality study.
Proper lifting has been a target for safe patient handling due to being a cheap and easy to implement intervention.The concept is to use proper body mechanics to limit the stress on the body, specifically on the spine, by keeping the patient close, bending the knees, and keeping the back upright.Biomechanical studies have shown a reduction in joint postures-more neutral postures (2 studies), trunk moments (3 studies), and spine loads (3 studies) when using proper lifting as compared to no training.Only one study found no difference in joint postures between proper lifting technique and nontraining lifting.Under controlled laboratory conditions (all have been rated medium quality), proper lifting appears to be effective in reducing the stresses on the body.Basically, healthcare givers were more upright and closer to the patient which reduced the trunk moments, muscle activity, and corresponding spine loads when using "proper lifting technique."However, caution should be taken as training has limitations in the real world when work demands are high, fatigue sets in, and returning to normal lifting.Most biomechanical laboratory studies utilize a compliant simulated patient that will often minimize the biomechanical responses for the caregivers (Marras et al., 1999).Sudden changes in the patient due to losing balance, sudden strength imbalance, or mental impairment may result in a sudden load on the caregiver who is holding them.Lifting or transferring a noncompliant patient is much different than compliant as sudden movements or dead weight of a patient can produce significant additional force requirements for the caregiver, oftentimes unexpected and rapidly.Further, Nelson and Baptiste (2006) provided significant evidence that proper lifting mechanics and safe lifting techniques are not effective in controlling injuries due to patient handling.The bottom line, there is no way to safely manually handle patients (Nelson et al., 2007;Wilson & Davis, 2016).Finally, there are relatively few biomechanical studies (only medium quality studies) investigating proper lifting training to really form a decisive conclusion on training effectiveness to protect caregivers during patient handling.
Slide boards and roller boards have been found relatively ineffective (no difference) with slightly more studies that found them to reduce the biomechanics as compared to manual lifting (25 reduced vs. 15 no difference) (Table 2).For many of the outcomes, slide/roller boards were found to be equivalent to manual handling.The two biomechanical outcome variables that did see consistent benefit of slide/roller boards were hand forces (7 studies found decrease hand forces, 1 no difference) and muscle activity (6 studies found decrease muscle activity, 1 no difference).These reductions in hand force and muscle activity do not seem to translate to reductions in trunk moments and spine loads.While the friction force between the boards and body are likely reduced, the caregiver must still move significant body weight.Further, the roller board devices are only viable during lateral transfers while slide boards can be utilized in lateral transfers and repositioning.The studies evaluating slide/roller boards were generally medium quality with two being medium-high quality and one high quality.The medium-high and high quality studies found decreases in shoulder and trunk flexion, reduced perceived effort, reduced hand forces, lower muscle activations, and low spine loading for slide board as compared to draw sheet (Budarick et al., 2020;Hwang et al., 2019Hwang et al., , 2020)).Overall, except for reducing hand forces, slide boards and roller boards appear to be a marginally viable solution in protecting caregivers during handling patients.
The use of a belt (gait or walkingbelts) has had mixed results for biomechanical outcomes.Belts have been shown to reduce nonneutral postures (5 studies) and hand forces (5 studies, 1 no difference), but to a lesser extent, limited impact on spine loads (5 studies decrease, 3 studies no difference, and 1 study increase).There were few studies that were rated medium quality investigating gait/walking belts, thus providing further support that belts have limited utility in patient handling.Studies for gait and walking belts have the same concerns as research for proper lifting technique as noncompliant patients can still pose significant risk for the caregiver.Furthermore, gait and walking belts are predominantly used during transfers of patients (e.g., bed to standing, bed to chair, bed to toilet, and bed to wheelchair) and are not applicable to repositioning and lateral transferring.With about equal as many studies finding no difference or worse results as lifting manually, gait and walking belts do not appear to be viable safe patient handling devices.
Friction reducing sheets or use of plastic bags have similar results to the slide/roller boards where these devices were effective in reducing the hand forces (4 studies found decrease, 2 found no difference) and muscle activity (6 studies found reduced, 1 study with no difference), These changes did appear to reduce the biomechanical loading on the spine (5 studies report decreases and 2 study no difference).Two medium-high quality studies (Hwang et al., 2019(Hwang et al., , 2020) ) found lower hand forces, less muscle activity, and lower spine loads for frictionless sheets as compared to manual lifting.Several medium rated quality studies found no difference in friction reducing sheets and manual lifting (Kotowski et al., 2022;Weiner et al., 2017).The friction reducing sliding devices can only be utilized for repositioning and lateral transferring of patients, not actual transfers in and out of bed.Overall, there appears some utility for these devices as they reduce the resistant forces between the bed and patient (e.g., friction and shear forces), ultimately reducing the biomechanical requirements and loads on the caregivers.
Air-assisted devices have been shown to be effective in reducing the biomechanical stress on the caregivers but are restricted to repositioning and lateral transfers.All but one study (trunk moments) revealed reductions in the outcomes when compared to manual handling (with decreases in 2 studies for postures, 5 studies for hand forces, 4 studies for muscle activity, 5 studies for spine loading, and 3 studies for trunk moments).Most of the studies investigating air-assisted devices were rated medium or better (Hwang et al., 2019(Hwang et al., , 2020;;Kotowski et al., 2022;Omura et al., 2022;Wiggermann et al., 2021) and yielded the positive results.These devices provide an air cushion between the body and bed/stretcher that allows the caregiver to easily slide the patient over the bed with minimal effort.One concern for these devices is the need to place the air mattress under the patient, which requires additional movement and handling (e.g., need to roll and place under patient and requiring manual movement of patient) or placing the air mattress under the patient when arriving at the facility and leaving under until needed.One concern with these air mattresses under the patient for long-term periods is concern for infection and bacteria control.The air mattress studies did not evaluate the biomechanical responses during the positioning of the air mattresses under the patient, but rather focused on the transfer and repositioning tasks.
Mechanical lifts, floor and ceiling, were found to be effective in reducing many of the biomechanical outcomes with few "no difference" outcomes (2 studies relating to positional outcomes) (see Table 2).All studies that investigated ceiling lifts found decreases in biomechanical outcomes, by far the most effective patient handling device.Most studies that compared floor lifts to ceiling lifts found ceiling lifts to be superior in reducing spine loads and trunk moments as well as other biomechanical outcomes (Dutta et al., 2011(Dutta et al., , 2012;;Marras et al., 2009;Santaguida et al., 2005;Waters et al., 2012).Ceiling lifts have also been found to be the preferred method for reducing actual injuries (Asuquo et al., 2021;Chhokar et al., 2005;Engst et al., 2005;Lee & Rempel, 2020;Villeneuve, 1998).Overall, mechanical lift studies were rated at medium or better quality and found lifts to be effective in reducing biomechanical loading, for all types of patient handling: transfers, repositions, and lateral transfers.
The review provides insight into the benefit of lifting devices as it was apparent that manual lifting was not safe, no matter how good your proper lift mechanics.Based on the current evidence, the best way to protect healthcare workers is to utilize lifts, preferably ceiling lifts.

Missing Evidence
There are several shortcomings of the current studies.First, there are several biomechanical outcomes that have had limited investigation.Most safe patient handling interventions have had limited physiological assessment that will provide evaluation of fatigue.Additionally, for any one intervention modality and specific biomechanical outcome, few studies were found (at most 7 studies) with most of these being rated medium-low to low quality (40 out of 56 studies, 71%).Second, all of the studies evaluated the patient handling intervention have concentrated on transfers (e.g., from bed), repositioning, and lateral transfers.Other handling tasks such as sitto-stand, turning patient in bed, limb lifting, and repositioning and some more high hazard activities like supporting people with limited balance and those that fall need to be investigated with respect to biomechanical outcomes.Third, there is a need for more comprehensive investigations that include basic biomechanical outcomes (e.g., hand forces, positions, and muscle activity) as well as more complex outcomes (e.g., joint moments and spine loads) as many of the studies relied on a single simple assessment.Fourth, one of the most disturbing results was that very few studies investigate nonnursing healthcare workers.With the focus on mobility now being undertaken by physical therapists (PT) or occupational therapists (OT), future studies need to understand the differences in patient handling demands for PT/OT versus nurses.Thus, the current review provides a plethora of evidence about many patient handling equipment but there remains a tremendous amount of future work that needs to be done for a more complete picture.

Limitations of the Review
There are several potential imitations that should be considered with the current review.First, the review only covers articles published in English.While most journals fall into this category, several additional studies may have been overlooked.Second, biomechanical outcomes are only one type of outcome that relates to safe patient handling.Other factors such as patient safety, patient comfort, risk of injury, cognitive demands, and time to complete the handling task should be reviewed for a more comprehensive understanding of patient handling devices.Finally, most of the studies included in this review were rated below high quality, which limits the ultimate understanding of the effectiveness of patient handling devices.Some people feel reviews should only contain the highest quality, but we wanted to include all biomechanical studies.Future research should strive to have high quality by including wellvalidated measures such as complex spine loading models, recruit actual healthcare workers for participants with large numbers, use an actual person simulating a noncompliant patient, and use a strong study design.

Conclusion
Current best practice guidelines adopted by many international governmental systems suggest that the use of assistive devices is an essential step to risk reduction for care workers.This review shows an increase in the volume of studies and higher quality evidence that the use of assistive devices does indeed reduce the physical loads on caregivers.This cumulative knowledge should support the increased use of suitable assistive devices in care delivery.Some areas of patient handling still require further investigation to further reduce the overload of care workers form specific transfers such as a sitto-stand, walking and falling patients, and other postural static loads that are evident in care work.↓ lift versus gait belt, sling, and 2-person manual; no difference for perceived stress for Hoyer lift versus twoperson manual ↓ lifts, sling, and gait and walking belt versus 2person manual for discomfort Garg et al., 1991b No difference between sling and gait walking belts versus 2-person manual for trunk posture ↓ lift, sling and walking belt versus 2-person manual for perceived stress;

Appendix
↑ Hoyer lift versus walking belt, sling, and 2-person manual for perceived stress ↓ lifts, sling and walking belt versus 2-person manual for discomfort (continued) ↓ compression with air-assisted device and friction reducing sheets versus draw sheet during lateral transfer Zhuang et al., 1999 ↓ hand force when placing sling and using ceiling lift versus manual with gait belt when positioning for transfer; ↑ hand force for trunk when stand-up lift and sliding board versus manual with gait belt when positioning for transfer ↓ compression when placing sling and using ceiling lift versus manual with gait belt when positioning for transfer • Proper body mechanic training was not sufficient in reducing the biomechanical load on caregivers.• Air-assisted devices reduced loading when repositioning and lateral transferring patients.

Figure 1 .
Figure 1.Schematic summary of the article search to identify articles included in the review (Figured adapted from Page and associates, 2021).

Table 1 .
Summary of Studies Included in the Biomechanical Review: Author, Date, Study Population, Country, Study Design, and Rating of Study Quality Measured muscle activity, trunk posture, and trunk moment during turning tasks in two turning directions (toward vs. Measured body postures and ground reaction forces and predicted trunk moments during transfers from wheelchair to bed using low back belt on patient, on caregiver, and on both away relative to caregivers) using five device conditions: Draw sheet, friction-reducing turning sheet, air-assisted transfer device, air-assisted turning device, and no assistive device United States Laboratory study: Measured hand force; shoulder and trunk posture; shoulder moment; muscle activity and usability ratings from four devices: a Draw sheet, a repositioning sheet, a slide board, and an air-assisted device during repositioning Medium-high Iridiastadi, Vani, Yamin 2020 12 nurses who worked at local hospital for at least a year Indonesia Laboratory study: Measured postural assessment, static spinal load, and perceived exertion from Borg scale Medium (continued) Medium Keir, MacDonell 2004 7 participants: 4 novice males, 1 experienced female, and 2 experienced males Canada Laboratory Study: Measured muscle activity patterns during manual transfers and transfers using floor and ceiling lifts Low-medium Koppelaar, Knibbe, Miedema, Burdorf 2012 186 nurses in nursing homes (179 females and 7 males)*Under Study Design, the table provides the assessments for the quality ratings: SPART-participants representative of population, CODATA-complete outcome data, CONFconfounders accounted for, BINT-Outcome assessors blinded to intervention, ADHERE-adherence to intervention, SUB20-sufficient numbers of subjects (N >20), VALMvalidated measures, REALPAT-realistic patients being moved, and REQUIP-reliable equipment.

Table 2 .
Summary of the Number of Studies That Found a Decrease (↓), No Difference, or Increase (↑) Relative to Manual or Draw Sheet and the Various Safe Patient Handling Equipment or Techniques for Each of the Outcomes

Table A1 .
Summary of the Quantitative and Subjective Results for Safe Patient Handling Interventions.

Table A2 .
Summary of the Biomechanical Loading Results for Safe Patient Handling Interventions.